We have a lot (1800) of warnings in compile process of our web application.
For dlls which used by web application it was solved by adding different alias for RedGate libraries. But this workaround is not useful for aspnet_compiler.
Also it is not possible to suppress this warning.

Could you help with it?

Warnings:

(0): warning CS1685: The predefined type 'System.Func' is defined in multiple assemblies in the global alias; using definition from 'c:\\Windows\\Microsoft.NET\\Framework64\\v4.0.30319\\mscorlib.dll'(0): warning CS1685: The predefined type 'System.Runtime.CompilerServices.ExtensionAttribute' is defined in multiple assemblies in the global alias; using definition from 'c:\\Windows\\Microsoft.NET\\Framework64\\v4.0.30319\\Temporary ASP.NET Files\\root\\ec8d7bb0\\fdb93028\\assembly\\dl3\\1811f998\\c5d5991c_b86fcd01\\LinqBridge.DLL'

Sorry to say there is no workaround for this issue - We had implemented something to extend Linq and then later Microsoft went and added the same class to .NET Framework.

However, you should be able to safely ignore the warning - it should not prevent the code from compiling unless "treat warnings as errors" is on. Not sure if that applies to aspnet_compiler but it may do.